Cloud computing is a technology in which dynamically scalable and virtualized resources are provided over the internet. By using cloud computing, a network can be conveniently accessed, and storage and management of massive data can be implemented by configuring a large number of storage devices. In cloud computing, a great number of users need to be involved, and to protect security of user data, a user generally encrypts user data to be uploaded to a cloud server.
However, when uploading encrypted user data to the cloud server, the user also uploads summary information of the user data at the same time, where the summary information is a brief summary of user data, and is information that describes the user data in a concise form by extracting key information from the user data; and the summary information may include a name, a phone number, an e-mail address, information that interests the user, and so on. Due to openness of the summary information, a third party may obtain, from the cloud server, summary information of a user in which the third party is interested. As a result, personal privacy information of the user is leaked, and security performance of a cloud computing system is reduced.